1. Field of the Invention
This invention relates to feeding a print medium into a printer and to guiding a print medium through a path in a printer.
2. Related Art
Many printers provide multiple operational modes in which a print medium (e.g., paper, plastic transparency) is fed into a print drive mechanism used to advance the print medium through a printing zone of the printer during printing. For example, the standard mode of operation of many desktop printers is an automatic multi-sheet feeding mode in which individual sheets from a stack of print media (held in, for example, a tray) are, upon appropriate electronic control (e.g., computer control), automatically picked from the stack by a pick mechanism and fed into the print drive mechanism. Many of those printers also include a secondary mode of operation, usually intended for occasional and/or specialized use. The secondary operational mode is often a single sheet mode in which a single sheet of a print medium is fed (often manually) into the print drive mechanism. The secondary operational mode is sometimes a mode in which a small number of sheets of print media are placed in a feed tray, and automatically picked and fed to a print drive mechanism.
Generally, in printers that include a secondary mode of operation in addition to a standard mode of operation, a print medium is fed into the print drive mechanism during the secondary operational mode in the same direction as that in which a print medium is fed during the standard operational mode. For example, in some printers, single sheet mode consists of nothing more than placing a single sheet of a print medium on a stack of print media used in an automatic multi-sheet feeding mode so that the added single sheet is the next sheet picked and fed into the print zone. Even in printers in which a print medium is initially fed into a physically separate loading slot during the secondary operational mode, the print medium is usually eventually directed into the print drive mechanism through the same feed path (i.e., in the same direction) as used during the standard operational mode.
Physical constraints may preclude location of a loading slot for a secondary operational mode so that the feed path for the standard operational mode can be used. For example, a printer designed to be operated within a small area or volume (i.e., a printer having a small form factor) may be restricted so that a user can only access the front of the printer, necessitating that a loading slot for manually feeding a print medium be placed at the front of the printer. If the printer is also designed so that, in the standard operational mode, sheets of print media are fed in a direction from the back of the printer to the front, it becomes, at best, impractical to feed a sheet from the manual feed loading slot into the print drive mechanism in the same direction as that in which sheets are fed during the standard operational mode.
In an inkjet printer, feeding a sheet of a print medium into a print drive mechanism of the printer in a direction opposite that in which sheets are fed into the print drive mechanism during standard operation can be problematic because, just prior to being fed into the print drive mechanism, the sheet must traverse the area (swath gap) through which the print cartridge(s) pass during printing. Since the sheet, which is typically thin and flexible, is not supported in this area, it can be difficult to ensure that the sheet is properly fed into the print drive mechanism. Similar problems (e.g., the necessity for a sheet of a print medium to traverse a gap in the feed path) can exist in other types of printers when a sheet of a print medium is fed into the print drive mechanism in other than the normal feed direction.
One inkjet printer enables a sheet of a print medium to be fed into a print drive mechanism of the printer in a direction opposite that in which sheets are fed into the print drive mechanism during a standard operational mode by providing a sheet feed drive mechanism for such sheet. The sheet feed drive mechanism is positioned opposite the print cartridge swath gap from the print drive mechanism. In a secondary operational mode, a sheet of a print medium is fed into the sheet feed drive mechanism which acts to guide and support the sheet as the sheet traverses the print cartridge swath gap. However, the addition of another drive mechanism significantly increases the cost and complexity of the printer. The additional drive mechanism also necessitates additional space so that the printer is larger than desirable. Additionally, in this printer, a user must effect a special control instruction to cause the sheet feed drive mechanism to operate to feed a sheet of a print medium; the user cannot simply insert the sheet in the feed path. Further, it may not be possible or desirable to feed a sheet of a print medium back through the additional drive mechanism immediately after printing on the sheet, since the ink on the sheet may not be dry. (This problem can be overcome by, for example, pausing during printing to let the ink dry before feeding the sheet through the additional drive roller, or by guiding the sheet through a different exit path using additional structure provided in the printer; neither solution is desirable.) Thus, a better solution is needed for situations in which it is necessary or desirable to provide a second, distinct feed path to a print drive mechanism in addition a first feed path, and, in particular, situations in which such a second feed path is positioned so that a print medium fed therethrough is fed into the print drive mechanism in a direction opposite that in which print media are fed into the print drive mechanism through the first feed path.
In a mode of operation in which a sheet of a print medium is manually fed into a printer, it is often necessary to detect the insertion of a sheet into the print medium feed path associated with that mode of operation. This is typically done by adding an electronic sensor, either an interrupter-type sensor or a reflective-type sensor, that is dedicated to the task of print medium insertion detection. The additional electronics add to the cost and complexity of the printer. An alternative solution to such print medium insertion detection that is more inexpensive and simple is desirable.